 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.runtime;

 /**
  * An extension declared in a plug-in.
  * All information is obtained from the declaring plug-in's
  * manifest (<code>plugin.xml</code>) file.
  * <p>
  * These registry objects are intended for relatively short-term use. Clients that
  * deal with these objects must be aware that they may become invalid if the
  * declaring plug-in is updated or uninstalled. If this happens, all methods except
  * {@link #isValid()} will throw {@link InvalidRegistryObjectException}.
  * For extension objects, the most common case is code in a plug-in dealing
  * with extensions contributed to one of the extension points it declares.
  * Code in a plug-in that has declared that it is not dynamic aware (or not
  * declared anything) can safely ignore this issue, since the registry
  * would not be modified while it is active. However, code in a plug-in that
  * declares that it is dynamic aware must be careful when accessing the extension
  * objects because they become invalid if the contributing plug-in is removed.
  * Similarly, tools that analyze or display the extension registry are vulnerable.
  * Client code can pre-test for invalid objects by calling {@link #isValid()},
  * which never throws this exception. However, pre-tests are usually not sufficient
  * because of the possibility of the extension object becoming invalid as a
  * result of a concurrent activity. At-risk clients must treat
  * <code>InvalidRegistryObjectException</code> as if it were a checked exception.
  * Also, such clients should probably register a listener with the extension registry
  * so that they receive notification of any changes to the registry.
  * </p><p>
  * This interface can be used without OSGi running.
  * </p><p>
  * This interface is not intended to be implemented by clients.
  * </p>
  */
 public interface IExtension {
     /**
      * Returns all configuration elements declared by this extension.
      * These elements are a direct reflection of the configuration
      * markup supplied in the manifest (<code>plugin.xml</code>)
      * file for the plug-in that declares this extension.
      * Returns an empty array if this extension does not declare any
      * configuration elements.
      *
      * @return the configuration elements declared by this extension
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      */
     public IConfigurationElement[] getConfigurationElements() throws InvalidRegistryObjectException;

     /**
      * Returns the namespace for this extension. This value can be used
      * in various global facilities to discover this extension's provider.
      *
      * @return the namespace for this extension
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      * @see IExtensionRegistry
      * @since 3.0
      * @deprecated As namespace is no longer restricted to the contributor name,
      * use {@link #getNamespaceIdentifier()} to obtain namespace name or {@link #getContributor()}
      * to get the name of the contributor of this registry element.
      * <p>
      * In the past namespace was dictated by the name of the bundle. If bundle <code>org.abc</code>
      * contributed registry element with Id of <code>MyId</code>, the namespace of
      * the element was always set to <code>org.abc</code>, producing the qualified name of
      * <code>org.abc.MyId</code>.
      * </p><p>
      * The namespace used to be the same as the bundle name. As a result, the {@link #getNamespace()}
      * method was used both to obtain the name of the bundle and to obtain the namespace of a registry
      * element.
      * </p><p>
      * Since 3.2, the extension registry allows elements to specify qualified name. The extension point
      * of the plug-in <code>org.abc</code> could specify <code>org.zzz.MyExtPoint</code> as
      * an Id. In this case, namespace name is <code>org.zzz</code>, but the contributor
      * name is <code>org.abc</code>.
      * </p><p>
      * (The use of a simple Id is still a preferred way. Whenever possible, specify only the simple
      * Id and let runtime take care of the rest.)
      * </p><p>
      * If your code used the {@link #getNamespace()} to obtain the name of the contributing bundle,
      * use {@link #getContributor()}. The typical usage pattern here is to find a bundle name to obtain
      * some information from the corresponding OSGi bundle. For example, deducing the file location
      * specified as a relative path to the bundle install location would fall into this group.
      * </p><p>
      * If your code used the {@link #getNamespace()} to obtain the namespace of the registry element,
      * use {@link #getNamespaceIdentifier()}. Typically, this is the case when code is trying to process
      * registry elements belonging to some logical group. For example, processing notifications for all
      * elements belonging to the <code>org.abc</code> namespace would fall into this category.
      * </p>
      */
     public String getNamespace() throws InvalidRegistryObjectException;

     /**
      * Returns the namespace name for this extension.
      *
      * @return the namespace name for this extension
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      * @since org.eclipse.equinox.registry 3.2
      */
     public String getNamespaceIdentifier() throws InvalidRegistryObjectException;

     /**
      * Returns the contributor of this extension.
      *
      * @return the contributor for this extension
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      * @since org.eclipse.equinox.registry 3.2
      */
     public IContributor getContributor() throws InvalidRegistryObjectException;

     /**
      * Returns the unique identifier of the extension point
      * to which this extension should be contributed.
      *
      * @return the unique identifier of the relevant extension point
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      */
     public String getExtensionPointUniqueIdentifier() throws InvalidRegistryObjectException;

     /**
      * Returns a displayable label for this extension.
      * Returns the empty string if no label for this extension
      * is specified in the plug-in manifest file.
      * <p> Note that any translation specified in the plug-in manifest
      * file is automatically applied.
      * <p>
      *
      * @return a displayable string label for this extension,
      * possibly the empty string
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      */
     public String getLabel() throws InvalidRegistryObjectException;

     /**
      * Returns the simple identifier of this extension, or <code>null</code>
      * if this extension does not have an identifier.
      * This identifier is specified in the plug-in manifest (<code>plugin.xml</code>)
      * file as a non-empty string containing no period characters
      * (<code>'.'</code>) and must be unique within the namespace.
      *
      * @return the simple identifier of the extension (e.g. <code>"main"</code>)
      * or <code>null</code>
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      */
     public String getSimpleIdentifier() throws InvalidRegistryObjectException;

     /**
      * Returns the unique identifier of this extension, or <code>null</code>
      * if this extension does not have an identifier.
      * If available, this identifier is unique within the plug-in registry, and
      * is composed of the namespace where this extension
      * was declared and this extension's simple identifier.
      *
      * @return the unique identifier of the extension
      * (e.g. <code>"com.example.acme.main"</code>), or <code>null</code>
      * @throws InvalidRegistryObjectException if this extension is no longer valid
      */
     public String getUniqueIdentifier() throws InvalidRegistryObjectException;

     /* (non-javadoc)
      * @see Object#equals(java.lang.Object)
      */
     public boolean equals(Object o);

     /**
      * Returns whether this extension object is valid.
      *
      * @return <code>true</code> if the object is valid, and <code>false</code>
      * if it is no longer valid
      * @since 3.1
      */
     public boolean isValid();
 }

